Patent GB-1083555-A (GB)
Title: Monitor system
IPC: G08B21/16
Filed: 1964-09-29
Abstract: 1,083,555. Photo-electric oil mist monitor system. STEWART-WARNER CORPORATION. Sept. 29, 1964 [Sept. 30, 1963], No. 39639/64. Heading G1A. In an oil mist distribution system means are provided for monitoring the optical density of the oil mist, comprising a light source and a detector responsive to light which has passed through the oil mist, the detector output being connected through an amplifier to two switching devices arranged to operate respectively at first and second amplifier output levels corresponding to predetermined upper and lower optical densities. Monitor unit construction. The source (49) and detector (45) are mounted in a monitor unit (22) which may be located near the output of an oil mist generator (10) Fig. 1 (not shown), but is preferably located close to a lubrication fitting (16). The unit (22) comprises a body (36), containing a transverse tubular portion (38) which can be inserted into the oil mist line, and closed by a cap member (34) and a cup-shaped cap (32). The lamp (49) and detector (45), which may be a photo-resistor, are located at either side of the transverse tube (38), in recesses, together with lenses (59) and gaskets (59a), so that they are protected from the oil unit. Oil is prevented from depositing on the lenses by means of a continuous air flow through ducts (57) and into the oil mist chamber (44). The pressure difference necessary to drive air into chamber (44) is adjusted by screws and spring means (88, 90, 92) thus altering the position of a diaphragm (54), which is subject on its top side to the pressure of mist-laden air by virtue of a connecting passage (60) from the chamber (44), and on the bottom side to clean air pressure, air entering this part of the unit from a duct (68) and through the valve assembly (66). A suitable pressure for scrubbing the lenses is given as about 2 inches of water. Circuit details. The alarm circuit, Fig. 6, in which the photo-cell and lamp are connected, is supplied through a transformer 128. The output from the detector passes through a ganged selected switch 100 to the amplifier, comprising triodes 104 and 118. Connected in the anode circuit of the amplifier 118 are two relays 120, 122 which operate on make contacts 120b, 122b or break contacts 120c, 122c to energize appropriate lamps 124, 126. Thus, when the oil mist in the monitor unit is at the desired or normal rate, the anode current is sufficient to energize only relay 122 and the green lamp is lit. With no mist flowing in the monitor, the consequent minimum photo-cell resistance results in neither relay operating and the red warning lamp is lit, whereas with too much mist both relays are actuated and the red lamp is again energized. Capacitors in parallel with the relay coils act in preventing spurious lighting due to puffs of dense or less dense mist. For calibration of the circuit, the selector switch is changed to bring an ammeter A into circuit across the Zener diode, 109, which stabilizes the amplifier. Thus the lamp intensity is adjusted by potentiometer 150, to suit the particular lubricant used, until the meter A reads the current value required for a normal density to be indicated (by energization of the green lamp). Alternatively, a potentiometer 115a in the amplifier circuit may be used to adjust the amplifier output to that for a normal optical density. The fail safe arrangement implicit in the circuit involves the red-lamp being energized through any malfunction of the system, together with the use of a battery supply.